Exploring the impact of caseload midwifery on preterm birth among vulnerable and disadvantaged women: a multi-centre randomised controlled trial

Women randomised to the caseload intervention will receive antenatal, intrapartum and early postpartum care from a primary caseload midwife (with one or two antenatal visits conducted by a ‘back-up’ midwife if necessary). Women will receive midwifery care as per hospital guidelines and in conjunction with other health providers e.g., Obstetricians, Physicians, Allied Health as required. The number, frequency and duration of antenatal visits will be as per care provision to all maternity consumers. The difference will be that, unlike other forms of maternity care, where the woman sees various (mostly unknown) midwives throughout the pregnancy, birth and postpartum periods, primary care provision for women assigned to the trial arm will be from the caseload midwife (with medical input as needed). Women in the intervention arm will also be able to contact their primary midwife (or back-up midwife) 24 hours a day, 7 days per week if needed, and the midwife will be on-call to provide care during the woman’s labour and birth. In the postpartum period, the known caseload midwife will provide postnatal care and feeding support to the woman and her baby in hospital and will visit them in their home on discharge for follow-up care and support. Therefore, women who receive the intervention will be provided with continuity of care from a known midwife throughout pregnancy, labour, birth and postpartum; women assigned to standard care will receive care throughout their pregnancy, labour, birth and postpartum from midwives who are working on that day, who may or may not be known to her. The frequency of visits, content of visits, location of visits will be the same in both arms – care will be otherwise provided according to the same hospital guidelines and protocols for all women. Data regarding the extent to which care was provided by the primary midwife will be collected primarily from the electronic medical record following the birth and from the women via telephone questionnaire at three months postpartum. To assess and compare continuity of carer, women in both trial arms will be asked about the presence of known care providers for labour, birth, postnatal hospital care and for their domiciliary care. All relevant hospital guidelines and protocols will be followed when providing care for women in this study, including, but not limited to the Royal Women’s Hospital guidelines - Labour and Birth and Early Puerperium – Care during 2018 - Standard Antenatal Check 2019 - Antenatal Care Schedule: hospital-led care 2020 - Postnatal Care and Documentation: Mother and Baby 2014 A nested sub-study will also explore the potential for differential physiological stress responses by trial arm at the Royal Women’s Hospital. Consecutively randomised English-speaking women recruited at one site (the Royal Women’s Hospital) will be offered participation to this nested sub-study. Heart rate variability, sAA and sC biomarkers will be measured at baseline (i.e., before 20 weeks of pregnancy) and in later pregnancy (i.e., at 36 weeks gestation). To determine a between-group difference at any single timepoint, 200 women are needed (allocation ratio 1:1) to achieve power of 0.80 and an effect size of 0.4. Allowing for some loss to follow-up, 240 women will be recruited (i.e., 120 women in each arm). Three biomarkers will be measured - a. salivary cortisol, b. salivary alpha-amylase, c. time and frequency domain heart rate variability using an electrocardiogram (ECG) recorder (i.e., Holter monitor). Salivary cortisol concentrations will be calculated (in ng/mL) using an enzyme-linked immunosorbent assay (ELISA). Salivary alpha-amylase activity will be assayed using a Kinetic Enzyme Assay Kit. Unstimulated saliva samples will be self-collected by women after waking by passing a cotton swab for each test around the mouth in a circular movement for one minute. Swabs will be provided to women who consent to participate at recruitment and, once self-collected, they will be posted to a laboratory at La Trobe university for processing using a registered post addressed envelope provided by the research team. Samples will be taken by women at 20 and 36 weeks gestation. Time and frequency domain heart rate variability will be measured on site by the research midwife following a scheduled pregnancy check-up (i.e., at recruitment and 36 weeks gestation). The research midwife will take women to a dimly lit, quiet room at the Royal Women’s Hospital for the assay (Room 10G, Chelsea House, 55 Flemington Road). Seated women will be fitted with an ECG recorder (Holter monitor), and asked to remain seated for an initial five minutes (familiarisation), then a further five minutes (rest). A five-minute cognitive test (to provoke a sympathetic autonomic response) will be conducted, then women will be asked to breathe in time to a metronome for five minutes at a rate of 20 breaths per minute (to initiate a parasympathetic response) and then to return to their normal (spontaneous) breathing pattern for five minutes. In total, this assay will take approximately 30 minutes to complete. Differences in salivary cortisol and salivary alpha-amylase concentrations and time and frequency domain heart rate variability between groups will be assessed at both timepoints to determine if there are differential physiological stress responses by trial arm.